4.2bsd IPC: UNIX or Internet domain better?

[Jim Shankland]

Someone recently said in this newsgroup that since the UNIX
domain is buggy (no arguments here!), it makes sense to use
the Internet domain for IPC on 4.2bsd, even if the communicating
processes are not on separate machines.  Whoever it was said that
this is no more expensive than using the UNIX domain; the software
is more robust; and, of course, the application generalizes trivially
to run over the network, if you ever want it to.

Problem is, according to my measurements, doing 32-byte writes
on a stream socket using the UNIX domain is about twice as fast
as using the Internet domain.  I tried this on a Microvax II running
Ultrix, and a CCI Power/6 running CCI's 4.2 port, with the same
results.  (They've taken all our vanilla 4.2 VAXen away to run
VAX/VMS.)  The two programs are identical, except for the stuff
that sets up the rendezvous.

Does anyone have an explanation for this?  Is there a trick to
making Internet sockets faster, when there's no actual networking
involved?  I'd like to use the Internet domain for my application,
but can't live with that kind of a performance penalty.

Jim Shankland
..!ucbvax!mtxinu!\
                  rtech!jas
 ..!ihnp4!cpsc6a!/